The ability to image underwater is highly desired for scientific and military applications, including optical communications, submarine awareness, diver visibility, and mine detection. Underwater imaging is severely impaired by scattering and optical turbulence associated with refractive index fluctuations. This work introduces a novel approach to restoration of degraded underwater imagery based on a multi-frame correction technique developed for atmospheric distortions. The method represents synthesis of "lucky-region" fusion with nonlinear gain and optical flow-based image warping. The developed multiframe image restoration algorithm is tested on underwater imagery collected in a laboratory tank and in a field exercise. Reliance of image restoration on accuracy of the optical flow algorithm is revealed. The developed algorithm demonstrates significant resolution improvement of the restored image in comparison to any single frame or the mean of the underwater image sequence.